For everyone's information:

We had a Windows 2008 / Vista hotfix get installed which broke CIFS access from our 2K8 Servers to the Netware CIFS shares.

We could map drives, but not access them. Any attempts to access a share (either by mapping or directly via UNC) would fail with a non-descript error message.

Turns out the culprit (at least at our site) was Hotfix KB955302.

If you are having troubles, try uninstalling that item. Fixed all of our Terminal Servers.